UNIVERSITY  OF  CALIFORNIA  PUBLICATIONS. 


COLLEGE  OF  AGRICULTURE. 


AGRICULTURAL  EXPERIMENT  STATION. 


SULFUR  SPRAYS 


RED  SPIDERS 


By  W.  H.  VOLCK. 


BULLETIN  No.  154 

(Berkeley,  June,  1903.) 


Red  Spider,  or  Mite  of  the 
Almond. 


SACRAMENTO: 

SUPI 

1903 


BENJAMIN  IDE  WHEELER,  Ph.D.,  LL.D.,  President  oj  the  University. 

EXPERIMENT  STATION  STAFF. 

E.  W.  HILGARD,  Ph.D.,  LL.D.,  Director  and  Chemist. 

E.  J.  WICKSON,  M.A.,  Horticulturist,  and  Superintendent  of  Central  Station  Grounds. 

W.  A.  SETCHELL,  Ph.D.,  Botanist. 

ELWOOD  MEAD,  M.S.,  C.E.,  Irrigation  Engineer. 

R.  H.  LOUGHRIDGE,  Ph.D.,  Agricultural  Geologist  and  Soil  Physicist.    (Soils  and  Alkali.) 

C.  W.  WOODWORTH,  M.S.,  Entomologist. 

M.  E.  JAFFA,  M.S.,  Assistant  Chemist.    (Foods,  Fertilizers.) 

G.  W.  SHAW,  M.A.,  Ph.D.,  Assistant  Chemist.    (Soils,  Beet-Sugar.) 

GEORGE  E.  COLBY,  M.S.,  Assistant  Chemist.    (Fruits,  Waters,  Insecticides.) 

RALPH  E.  SMITH,  B.S.,  Plant  Pathologist. 

A.  R.  WARD,B.S.A.,D.V.M.,  Veterinarian,  Bacteriologist. 

E.  H.  TWIGHT,  B.Sc,  Diploma  E.A.M.,  Viticulturist. 

E.  W.  MAJOR,  B.Agr.,  Dairy  Husbandry. 

A.  V.  STUBENRAUCH,  M.S.,  Assistant  Horticulturist  and  Superintendent  of  Substations. 

WARREN  T.  CLARKE,  B.S.,  Assistant  Field  Entomologist. 

H.  J.  QUAYLE,  B.S.,  Assistant  Entomologist. 

H.  M.  HALL,  M.S.,  Assistant  Botanist. 

GEORGE  ROBERTS,  M.S.,  Assistant  Chemist,  in  charge  Fertilizer  Control. 

C.  A.  TRIEBEL,  Ph.G.,  Student  Assistant  in  Agricultural  Laboratory. 

C.  A.  COLMORE,  B.S.,  Clerk  to  the  Director. 


EMIL  KELLNER,  Foreman  of  Central  Station  Grounds. 

JOHN  TUOHY,  Patron,  ) 

y  Tulare  Substation,  Tulare. 
JULIUS  FORRER,  Foreman,  ) 

R.  C.  RUST,  Patron,  ) 

V  Foothill  Substation,  Jackson. 
JOHN  H.  BARBER,  Foreman,  ) 

S.  D.  MERK,  Patron,  ) 

y  Coast  Range  Substation,  Paso  Robies. 
J.  H.OOLEY,  Workman  in  charge,  ) 

S.  N.  ANDROUS,  Patron,  )  (  Pomona 

y  Southern   California  Substation,  < 
J.  W.  MILLS,  Foreman,     )  (  Ontario. 

V.  C.  RICHARDS,  Patron, 

T.  L.  BOHLENDER,  in  charge, 

ROY  JONES,  Patron, 

WM.  SHUTT,  Foreman, 


y  Southern   California  Substation,  ■] 

1 
y  Forestry  Station,  Santa  Monica. 


The  Station  publications  (Reports  and  Bulletins),  so  long  as  available, 
will  be  sent  to  any  citizen  of  the  State  on  application. 


SULFUR  SPRAYS  FOR  RED  SPIDERS. 


The  present  Bulletin  is  based  on  the  results  obtained  in  the  cooperative  investigations 
of  the  Los  Angeles  County  Board  of  Horticultural  Commissioners,  the  Sutter  County 
Board  of  Horticultural  Commissioners,  and  the  Entomological  Department  of  the 
Experiment  Station.  Mr.  Volck,  a  student  in  entomology  at  the  University,  working 
under  the  direction  of  the  Entomologist,  served  as  inspector  in  the  two  counties  while 
the  investigations  here  reported  were  being  conducted.  Special  acknowledgments  for 
assistance  are  due  to  Mr.  J.  W.  Jeffreys,  secretary  of  the  Los  Angeles  Board ;  to  Messrs. 
Payne  and  Seeley,  Horticultural  Inspectors  of  Los  Angeles  County ;  and  to  Messrs. 
Stabler,  Kells,  and  Hull,  Horticultural  Commissioners  of  Sutter  County.  The  formulae 
now  offered  seem  to  meet  all  the  requirements  for  the  successful  control  of  these  pests 
on  both  citrus  and  deciduous  trees. 

C.  W.  WOODWORTH. 

Red  spiders  (a  family  of  plant-feeding  mites)  appear  as  minute 
brownish-red,  red,  or  yellow  specks,  found  either  moving  about  over  the 
surface  of  the  leaves  or  resting  in  protected  places  on  the  stems. 
Their  eggs  can  easily  be  seen  with  a  magnifying  glass.     In  the  case  of 


I      J 


FIG.  1.    The  Eggs,  Shed  Skins,  and  Molting  Forms  of  the  Red  Spider  of  the  Almond. 

the  red  spider  of  the  orange,  they  will  be  found  in  numbers  along  the 
mid-rib  on  the  upper  side  of  the  leaves,  but  are  often  found  elsewhere. 
They  are  round,  red  before  hatching,  and  white  afterward.  The  eggs  of 
the  almond  Bryobia  are  also  red,  but  are  usually  deposited  on  the  stems. 
The  larger  white  specks  and  masses  found  on  leaves  and  stems  infested 
with  mites,  are  composed  of  the  shed  skins  of  the  young  mites,  for  they 
molt  several  times  before  reaching  the  adult  stage. 


4  UNIVERSITY    OF   CALIFORNIA — EXPERIMENT   STATION. 

Mites  feed  by  sucking;  they  pump  out  the  more  liquid  parts  of  living 
cells  and  the  chlorophyll  or  green  bodies  suspended  in  them.  As  the 
injury  proceeds,  the  leaves  become  whiter  and  are  finally  killed  and  fall 
to  the  ground. 

THE   USE    OF    SULFUR. 

Ever  since  the  control  of  mites  has  been  attempted,  sulfur  in  various 
forms  has  been  one  of  the  principal  remedial  agents  employed.  This 
use  of  sulfur  antedates  entomological  records,  and  the  persistency  with 
which  it  has  been  followed  is  a  strong  indorsement  of  its  efficiency. 

Sulfur  has  been  found  especially  adapted  to  the  treatment  of  mites 
feeding  on  living  plants,  first,  because  of  its  efficiency  in  destroying  the 
mites;  and,  second,  because  of  its  very  neutral  behavior  toward  foliage. 

Our  own  experiments  were  made  on  two  species  of  mites  commonly 
called  red  spiders,  belonging  to  different  genera — the  Bryobia  of  the 
almond  and  other  deciduous  trees,  and  the  Tetranychus  on  orange,  which 
has  also  been  called  the  purple  orange  mite. 

The  orange  mite  is  best  adapted  to  experimental  work,  since  it  devel- 
ops readily  in  cells  constructed  on  oranges  or  other  citrus  fruits.  Mites 
were  inclosed  in  cells  with  very  small  amounts  of  sublimed  sulfur,  and 
check  cells  were  provided  in  which  no  sulfur  was  placed.  In  every  case 
the  mites  inclosed  with  sulfur  either  died  shortly  after  exposure,  or  laid 
a  few  eggs  which,  while  hatching,  never  reached  maturity.  In  the 
check  cells,  however,  the  mites  prospered  as  long  as  the  food  supply 
lasted. 

The  record  of  one  of  these  experiments  is  inserted  here  to  show  the 
gradual  manner  in  which  sulfur  acts — some  time  elapsing  after  applica- 
tion before  the  full  effect  is  obtained. 

On  the  20th  of  October,  1902,  mites  were  inclosed  in  seven  cells,  four 
of  which  were  checks  and  three  contained  a  small  amount  of  sulfur. 
On  the  18th  of  November  18  per  cent  of  mites  were  alive  in  the  sulfured 
cells,  while  in  the  checks  64  per  cent  were  still  alive.  The  average 
number  of  eggs  laid  in  the  sulfured  cells  was  nineteen,  while  in  the 
checks  it  was  fifty. 

Similar  experiments  were  also  tried  with  foliage.  Small  mite-infested 
branches  were  dusted  with  sublimed  sulfur  and  inclosed  in  paper  bags 
without  severing  from  the  tree.  In  less  than  a  month,  the  only  traces 
of  living  mites  were  a  very  few  eggs  and  newly-hatched  young. 

DRY    SULFURING. 

Dry  sulfuring,  or  dusting  with  ground  or  with  sublimed  sulfur,  has 
been  the  usual  method  of  application.  The  conditions  determining  the 
success  of  dry  sulfur  are,  first,  the  thorough  distribution  of  the  material 
over  the  entire  surface  of  the  tree;  and,  second,  the  retention  of  this 
sulfur  for  a  period  sufficient  to  allow  it  to  act  both  on  the  mites  present 


SULFUR    SPRAYS    FOR    RED    SPIDERS.  5 

at  the  time  of  application,  and  on  those  which  will  hatch  from  the  eggs 
always  to  be  found  in  large  numbers  on  infested  plants. 

With  dry  sulfuring  these  conditions  are  often  but  imperfectly  met. 
The  retention  of  sulfur  offers  the  greatest  difficulty.  It  is  best  accom- 
plished by  dusting  the  trees  when  they  are  wet  with  dew,  but  even  then 
the  results  are  not  always  satisfactory,  since  large  areas  of  the  foliage 
may  become  nearly  free  from  sulfur,  again  allowing  the  mites  to  increase. 
Therefore,  dry  sulfuring,  as  generally  practiced,  can  only  be  regarded  as 
a  method  of  partial  control,  and  has  proved  a  failure  in  certain  refractory 
oases ;  indeed,  it  has  seldom  been  at  all  successful  against  the  red  spider 
of  the  orange  in  southern  California,  because  this  mite  does  most  of  its 
work  in  the  fall,  winter,  and  spring,  when  rains  and  winds  greatly 
reduce  the  chances  of  dry  sulfur  adhering  long  enough  to  be  effective. 

It  is  evident  that  neglecting  to  apply  the  sulfur  thoroughly  when 
the  trees  are  wet  will  greatly  reduce  the  chances  of  success,  and  may 
often  result  in  failure.  The  practice  of  dusting  the  ground  under  the 
trees,  or  dusting  the  spider  webs  found  on  the  ground,  will  have  little  or 
no  effect. 

Our  red  spiders  lay  their  eggs  and  spend  their  entire  life  on  the 
infested  plants.  As  far  as  we  have  been  able  to  ascertain,  they  do  not 
intentionally  go  to  the  ground  at  any  time,  but  when  they  become  very 
numerous  on  infested  trees,  they  may  be  knocked  off  or  fall  with  the 
dropping  leaves  in  sufficient  numbers  to  be  noticeable  on  the  ground, 
where,  without  doubt,  the  great  majority  die  of  starvation,  being  unable 
to  find  their  way  back  to  the  tree.  The  web  found  on  the  ground,  and 
the  greater  part  of  that  on  the  trees,  is  the  work  of  true  spiders  and 
not  mites;  these  true  spiders  catch  insects  and  are  beneficial. 

The  above  remarks  refer  to  the  red  spiders  of  the  almond  and  orange 
and  most  other  mites,  but  it  may  be  that  the  Tetranychus,  which  is 
known  as  the  yellow  mite,  spends  the  winter  on  native  green  plants, 
ascending  the  trees  in  the  spring. 

SULFUR    SPRAYING. 

Our  attention  was  first  called  to  the  advantages  of  the  wet  method 
of  applying  finely  divided  sulfur  by  a  grower  at  Upland,  who  mixed 
sulfur  into  water  by  constant  agitation  and  applied  it  as  a  spray  to  a 
considerable  number  of  orange  trees,  with  very  satisfactory  results. 
The  distribution  had  been  much  better  than  was  possible  with  a  dusting 
method,  but  the  adhering  qualities  were  not  good.  It  was  evident  that 
if  this  difficulty  could  be  overcome,  much  might  be  expected  of  this 
spray  as  a  remedy  for  mites. 

Several  adhesive  materials  were  added  to  the  mixture.  Lime,  which 
has  long  been  used  in  paris  green  work,  was  rejected  because  of  the  bad 
appearance  produced  when  used  on  citrus  trees.     After  numerous  trials 


6 


UNIVERSITY    OF   CALIFORNIA EXPERIMENT    STATION. 


flour  paste  prepared  according  to  a  definite  formula  was  adopted.  If 
the  flour-paste  spray  has  sufficient  time  to  dry,  it  withstands  rain  and 
winds  very  well.  Prolonged  rains  will  cause  some  shifting  of  the 
sulfur  particles,  but  these  set  again  on  drying. 

Sulfur  alone  requires  some  time  for  its  complete  effects  to  develop,  so 
if  rapid  disinfection  as  possible  is  desired  it  can  be  used  in  connection 
with  some  contact  insecticide.  For  this  purpose  sulfid  of  potash  has 
proved  best  adapted;  it  kills  by  contact,  but  has  no  lasting  effect. 


THE  TREATMENT  OF  THE  ORANGE  MITE  (RED  SPIDER). 

The  orange  tree  is  very  difficult  to  treat  satisfactorily,  and  very  few 
sprays  are  adapted  to  citrus  conditions;  the  difficulty  being  the  danger 
of  injuring  the  fruit  rind  or  the  leaves,  or  both.  Even  dry  sulfur  may 
be  harmful  if  applied  in  such  a  manner  as  to  leave  large  blotches  lodged 
on  the  young  fruit,  in  which  case  serious  burning  of  the  rind  may  result. 


FIG 


The  Red  Spider  of  the  Orange. 


The  injury  is  doubtless  due  to  the  presence  of  sulfuric  acid  in  the 
sulfur.  All  powdered  sulfur  contains  more  or  less  sulfuric  acid,  owing 
to  gradual  oxidation  by  contact  with  the  air.  In  the  preparation  of  the 
sulfur  spray  for  the  orange  mite  the  acid  may  be  neutralized  with  a 
small  amount  of  lime  or  better,  by  the  addition  of  sulfid  of  potash. 

During  the  fall  and  winter  of  1902  the  writer  treated  about  one  hun- 
dred orange  trees,  that  were  affected  by  the  mite,  with  the  sulfur  spray. 
The  results  were  entirely  satisfactory,  as  the  trees  and  fruit  were  not 
injured  by  the  application,  while  the  mites  were  very  greatly  reduced, 
and  possibly  exterminated  in  some  cases. 

Both  sublimed  and  ground  sulfur  were  used  with  good  results.  Some- 
what more  ground  sulfur  was  required,  since  part  of  it  is  in  very  coarse 


SULFUR    SPRAYS    FOR    RED    SPIDERS.  / 

particles,  and  so  not  available;  the  amounts  of  sulfur  varied  between 
10  and  20  pounds  to  100  gallons  of  water.  It  was  found  that  15  pounds 
of  sublimed  sulfur  per  100  gallons  were  ample  as  a  fall  or  winter  wash, 
while  10  pounds  would  do  just  as  well  in  the  spring,  after  the  danger  of 
prolonged  rains  is  over.  The  proportion  of  paste  found  most  satisfac- 
tory was  at  the  rate  of  4  pounds  of  wheat  flour  to  100  gallons  of  water. 
Much  more  than  this  causes  loss  by  scaling  off  of  the  paste  film,  and 
a  less  amount  will  not  be  sufficient  to  stick  the  sulfur.  The  lime  used 
to  neutralize  the  acid  was  slaked  and  strained  and  not  more  than 
1  pound  used  to  100  gallons  of  spray. 

The  application  of  this  spray  was  very  thorough;  the  trees  were  large 
Navels,  and  an  average  of  13  gallons  of  spray  was  used.  Great  care 
was  taken  to  wet  the  under  sides  of  the  leaves  and  fruit,  as  well  as  the 
stems  and  interior.  Some  of  the  trees  treated  were  under  observation 
for  over  a  month,  and  passed  through  heavy  rains  without  material  loss 
of  sulfur.  The  trees  were  not  sprayed  in  a  solid  block,  but  alternate 
rows  were  taken,  so  that  untreated  trees  remained  throughout  the 
treated  area.  The  result  was  that  in  less  than  a  month  the  treated 
trees  were  practically  clean,  while  the  checks  were  still  well-infested. 

Some  attention  was  paid  to  the  removal  of  the  sulfur  from  the  fruit, 
and  it  was  found  that  dry  brushing,  as  ordinarily  practiced  to  clean  off 
dust,  was  sufficient. 

Since  the  work  at  Azusa  was  completed  the  horticultural  inspector  at 
Monrovia  has  used  this  spray  on  a  larger  number  of  trees,  and  reports 
very  perfect  results.  It  ma}'  be  added  that  the  sulfur  spray  prepared 
by  the  formula  used  has,  so  far  as  observed,  no  injurious  effect  on  the 
tree  or  fruit,  and  can  be  applied  at  any  time  without  danger. 

SULFUR    SPRAYING    FOR   THE    ALMOND    MITE    (RED    SPIDER ). 

The  red  spider  of  almonds  and  prunes  is  a  serious  pest  in  the  interior 
valleys  of  California,  but  in  general  dry  sulfuring  has  proved  sufficiently 
effective  to  keep  it  in  check,  and  where  persisted  in,  whether  the  spider 
is  present  in  numbers  or  not,  has  resulted  in  the  practical  cleaning  up 
of  some  orchards. 

While  this  is  true  in  general,  there  are  a  few  cases  in  which  dry  sul- 
furing has  proved  a  failure.  The  most  refractory  case  known  was  that 
of  the  McMilin  almond  orchard  in  Sutter  County  ;  and  owing  to  the 
cooperation  of  the  County  Board  of  Horticultural  Commissioners,  we 
have  been  able  to  test,  on  an  entirely  different  mite  and  under  different 
climatic  conditions,  the  formula  developed  in  southern  California. 

The  red  spider  of  the  almond  is  larger  and  harder-bodied  than  the 
orange  species,  and  experiments  have  shown  it  to  be  about  four  times 
as  resistant  to  insecticides.  For  this  reason  and  also  because  the  mites 
were  very  numerous  and  doing  a  large  amount  of  injury  every  day,  it 
was  decided  to  use  sulfid  of  potash  with  the  sulfur  spray. 


8  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT   STATION. 

Two  gallons  of  the  stock  solution  (made  according  to.  the  formula 
given  below)  were  used  to  100  gallons  of  mixture.  The  paste  was  used 
in  the  same  proportions  as  in  spraying  orange  trees.  Sublimed  sulfur 
was  used  in  two  strengths — 10  and  20  pounds  to  100  gallons  of  mixture. 

Every  effort  was  made  to  spray  the  trees  thoroughly  on  both  the 
upper  and  lower  surfaces  of  the  twigs  and  leaves.  Trees,  15  to  20  feet 
in  diameter,  received  from  8  to  12  gallons  of  spray;  the  trees  were  in 
full  leaf,  so  the  amount  was  not  excessive. 

This  entire  orchard  was  treated  and  the  work  has  now  been  under 
observation  for  over  a  month.  The  injury  being  done  by  the  mite  was 
stopped  at  once,  the  majority  being  killed.  The  adults  all  died  in  about 
fifteen  days.  Very  few  eggs  remain,  and  the  sulfur  is  killing  the  young 
as  fast  as  they  hatch ;  in  fact,  it  seems  as  if  complete  disinfection  of 
many  trees  would  result. 

At  the  time  of  spraying,  the  leaves  of  many  of  the  trees  were  bleached 
out  by  the  constant  work  of  the  spider;  since  the  spraying,  the  color  of 
these  affected  leaves  has  improved  until  many  of  them  can  not  be  recog- 
nized as  mite-injured.  This  is  due  to  the  fact  that  mites  feed  by  suck- 
ing, and  their  mouth  parts  are  so  small  that  they  can  puncture  the  cells 
of  the  leaf  and  draw  off  the  more  fluid  portions,  including  the  green 
matter,  without  killing  them.  Microscopic  sections  of  leaves  very  badly 
injured  by  mites  show  the  cells  to  be  intact,  except  that  most  of  the 
chlorophyll  granules  have  been  removed.  These  results  show  that  the 
foliage  can  be  saved  even  in  very  advanced  cases  of  mite  injury. 

THE    SULFUR    SPRAY    COMPARED   WITH    DISTILLATES. 

Contact  sprays  can  not  compare  with  the  sulphur  spray  as  a  remedy 
for  mites,  for  when  properly  applied,  the  sulfur  spray  remains  active 
for  a  sufficient  length  of  time  to  kill  the  young  as  they  hatch  from  the 
egg,  and  may,  as  before  stated,  result  in  complete  disinfection. 

Of  the  contact  sprays,  the  distillates  are  perhaps  the  most  efficient, 
and  the  eggs  of  the  red  spider  of  the  orange  are  readily  killed  by  them. 
But  no  matter  how  thorough  the  application,  some  mites  and  eggs  will 
escape  contact  with  the  spray  mixture;  the  mites  thus  left,  because  of 
their  wonderful  reproductive  powers,  will  soon  increase,  making  another 
treatment  necessary.  This  repeated  treatment  with  oily  sprays  will 
prove  injurious  to  the  trees,  and  is  not  advisable  if  a  better  remedy  is 
available. 

The  effects  of  sulfur  on  higher  plants  is  so  slight,  if  any,  that  it 
has  never  been  serious  enough  to  attract  the  attention  of  the  most 
careful  observers. 

There  are  two  theories  to  explain  the  insecticidal  and  fungicidal 
properties  of  sulfur.  The  action  is  most  probably  due  to  the  vapor  of 
sulfur;  others  attribute  it  to  that  vapor  being  oxidized,  by  the  action  of 


SULFUR    SPRAYS    FOR    RED    SPIDERS. 


9 


the  air,  into  sulfurous  acid.  The  deadly  properties  of  sulfurous  acid,  or 
sulfur  smoke,  are  well  known,  and  it  is  usually  considered  to  be  more 
fatal  to  plant  than  to  animal  life.  Whichever  theory  is  correct,  it  is 
quite  certain  that  the  sulfur  has  to  evaporate  before  it  becomes  effective; 
therefore  the  larger  the  evaporating  surface,  the  better  the  result. 

The  evaporating  surface  of  a  substance  is  enormously  increased  by 
pulverizing  it  into  a  fine  powder,  and  the  finer  the  powder  the  greater  the 
surface.  There  is  no  reason  why  the  ground  sulfur  should  not  be  as  good 
as  the  sublimed,  if  the  pulverization  were  as  fine;  but  the  ground  sulfur 
on  the  market  is  composed  of  some  particles  very  much  finer  than 
the  particles  of  sublimed  sulfur,  and  many  others  vastly  coarser.  If 
these  large  particles  were  bolted  out  and  repulverized,  an  article  supe- 
rior to  sublimed  sulfur  might  be  produced. 


GROUND.  SUBLIMED. 

FIG.  3.    Photo-micrograph  of  Ground  and  Sublimed  Sulfur. 

The  left  side  of  the  accompanying  illustration  shows  the  irregular 
lumps  and  particles  of  ground  sulfur;  the  right  side  shows  the  uniform 
globular  bodies  of  sublimed  sulfur  collected  in  small  masses. 

If  the  efficiency  of  sulfur  depends  on  the  part  vaporized,  it  is  evident 
that  good  results  demand  the  retention  of  the  vapor.  This  could  be 
accomplished  by  placing  a  tent  over  the  tree,  as  in  cyanide  fumigation; 
but  the  time  required  for  sulfur  to  affect  mites  is  so  great,  that  this  is 
impracticable.  The  same  result  can  be  obtained  by  a  uniform  and 
thorough  distribution  of  the  sulfur  particles  over  the  surface  of  the  tree; 
when  this  has  been  accomplished,  the  mites  will  always  be  in  close 
proximity  to  particles  giving  off  vapor. 


10  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

PREPARATION  OF   SULFUR  SPRAYS. 

The  ingredients  of  the  sulfur  sprays  are  prepared  as  follows: 
Flour  Paste. — Take  one  pound  of  wheat  flour  to  one  gallon  of  water. 
Place  the  flour  in  a  box  with  a  screen  bottom  (common  window  screen- 
ing), and  pour  the  water  through  it,  until  all  the  flour  has  been  washed 
into  the  receiving  vessel.  It  will  then  be  finely  divided  and  free  from 
lumps.  The  mixture  should  then  be  brought  to  the  boiling  point,  being 
stirred  constantly,  thus  forming  a  thin  paste,  without  lumps. 

The  paste  is  conveniently  made  in  20-gallon  lots,  using  the  common 
25-gallon  kettles  so  often  found  on  California  ranches;  if  large  kettles 
are  not  available,  the  paste  can  be  boiled  in  less  water  and  then  diluted 
to  the  above  proportions  before  cooling.  The  paste  should  be  strained 
before  using. 

Sulfid  of  Potash  Stock  Solution. — Granulated,  or  powdered  concen- 
trated lye,  15  pounds;  sulfur,  18  pounds;  water  to  make  20  gallons.  Stir 
the  sulfur  and  lye  together  in  a  vessel  which  will  allow  plenty  of  room  for 
boiling.  When  well  mixed,  add  about  one  pint  of  water,  placing  it  in 
a  slight  hollow  in  the  mixture,  and  stir  in  slowly.  The  mixture  will 
soon  begin  to  melt  and  boil,  forming  a  red  fluid;  stir  until  the  boiling 
ceases,  and  then  add  water  to  make  20  gallons.  This  stock  solution  will 
keep  for  awhile,  or  indefinitely  when  protected  from  the  air. 

Preparation  of  the  Spray  Mixture  with  Sulfid  of  Potash. — Place  10  to 
15  pounds  of  sublimed  sulfur,  or  14  to  20  pounds  of  ground  sulfur  in  the 
spray  tank  with  4  gallons  of  flour  paste  and  1  to  2  gallons  of  the  sulfid  of 
potash  stock  solution;  add  water  to  make  100  gallons.  For  summer  or 
spring  spraying  after  the  danger  of  rains  is  over,  the  minimum  amount 
of  sulfur  is  sufficient. 

Without  Sulfid  of  Potash. — Made  as  before,  except  that  the  sulfid  of 
potash  is  omitted. 

The  sulfid  of  potash  is  not  necessary  to  kill  the  red  spider  of  the  orange, 
but  will  neutralize  any  sulfuric  acid  that  may  be  present.  One  gallon 
of  the  stock  solution  will  be  sufficient.  It  can  be  omitted  with  the  red 
spider  of  the  almond  if  the  application  be  made  in  time;  that  is,  before 
the  injury  has  become  very  serious. 

The  ingredients  of  the  sulfur  spray  must  be  kept  constantly  and 
strongly  agitated  while  in  use.  A  common  garden  hoe  is  a  good  instru- 
ment to  stir  with  in  hand  outfits,  especially  where  the  opening  in  the 
tank  is  small.  When  used  to  agitate  the  mixture  the  blade  of  the  hoe 
should  be  turned  up,  but  when  used  to  scrape  the  sulfur  from  the  bottom 
of  the  tank  the  blade  should  be  held  down  as  in  hoeing. 

A  power  outfit  provided  with  a  mechanical  agitator  is  very  desirable 
in  working  with  this  spray. 


SULFUR   SPRAYS    FOR   RED    SPIDERS.  11 

Spray  Nozzles. — In  our  experience  nozzles  of  the  plug-cock  type,  which 
can  be  cleaned  by  the  simple  turning  of  a  valve,  are  best  adapted  for 
the  sulfur  spray. 

Method  of  Spraying. — Much  of  the  success  of  any  spraying  operation 
depends  upon  the  thoroughness  of  the  application.  With  the  sulfur 
spray,  every  effort  should  be  made  to  wet  both  the  upper  and  the  lower 
surfaces  of  both  leaves  and  twigs  and  also  the  interior  of  the  tree.  This 
is  best  accomplished  by  beginning  at  the  top  and  working  the  spray 
well  through  the  upper  branches,  finishing  with  the  lower  parts.  This 
method  should  be  followed  around  the  tree,  lapping  well  over  the  section 
sprayed  at  the  beginning. 

The  sulfur  spray  is  cheap,  and  material  should  not  be  spared. 

A  symmetrical  almond  tree  20  feet  in  diameter  will  take  from  12  to  14 
gallons  of  spray,  and  an  orange  tree  of  the  same  size,  from  14  to  18 
gallons. 

SUMMARY. 

The  old  idea  that  sulfur  is  a  good  remedy  for  mites  is  fully  supported 
by  recent  experiments. 

Dry  sulfur  is  usually  successful  as  a  method  of  partial  control. 

Sulfur  spraying  has  been  found  many  times  more  efficient  than  other 
methods  of  application  and  is  perfectly  successful  where  dry  sulfuring 
has  failed. 

The  efficiency  of  the  sulfur  spray  has  been  demonstrated  for  the  red 
spider  of  the  orange  (Tetranychus  mytilaspidis)  in  southern  California, 
and  for  the  almond  Bryobia  in  Sutter  County. 


REPORTS  AND  BULLETINS  AVAILABLE  FOR  DISTRIBUTION. 


REPORTS. 


1896.  Report  of  the  Viticultural  Work  during  the  seasons  1887-93,  with  data  regarding 

the  Vintages  of  1894-95. 

1897.  Resistant  Vines,  their  Selection,  Adaptation,  and  Grafting.    Appendix  to  Viti- 

cultural Report  for  1896. 

1898.  Partial  Report  of  Work  of  Agricultural  Experiment  Station  for  the  years  1895-96 

and  1896-97. 
1900.    Report  of  the  Agricultural  Experiment  Station  for  the  year  1897-98. 
1902.    Report  of  the  Agricultural  Experiment  Station  for  1898-1901. 

BULLETINS. 

No.  115.  Remedies  for  Insect  and  Fungi.    (Revised.) 

121.  The  Conservation  of  Soil  Moisture  and  Economy  in  the  Use  of  Irrigation  Water. 

125.  Australian  Saltbush. 

127.  Bench-Grafting  Resistant  Vines. 

128.  Nature,  Value,  and  Utilization  of  Alkali  Lands. 

129.  Report  of  the  Condition  of  Olive  Culture  in  California. 

131.  The  Phylloxera  of  the  Vine. 

132.  Feeding  of  Farm  Animals. 

133.  Tolerance  of  Alkali  by  Various  Cultures. 

134.  Report  of  Condition  of  Vineyards  in  Portions  of  Santa  Clara  Valley. 

135.  The  Potato-Worm  in  California. 

136.  Erinose  of  the  Vine. 

137.  Pickling  Ripe  and  Green  Olives. 

138.  Citrus  Fruit  Culture. 

139.  Orange  and  Lemon  Rot. 

140.  Lands  of  the  Colorado  Delta  in  Salton  Basin,  and  Supplement. 

141.  Deciduous  Fruits  at  Paso  Robles. 

142.  Grasshoppers  in  California. 

143.  California  Peach-Tree  Borer. 

144.  The  Peach-Worm. 

145.  The  Red  Spider  of  Citrus  Trees. 

146.  New  Methods  of  Grafting  and  Budding  Vines. 

147.  Culture  Work  of  the  Substations. 

148.  Resistant  Vines  and  their  Hybrids. 

149.  California  Sugar  Industry. 

150.  The  Value  of  Oak  Leaves  for  Forage. 

151.  Arsenical  Insecticides. 

152.  Fumigation  Dosage. 

153.  Spraying  with  Distillates. 

Copies  may  be  had  by  application  to  the  Director  of  the  Experiment 
Station,  Berkeley,  California. 


